The Archdiocese of Washington has a FAQ that includes the following:
Is the Archdiocese of Washington the headquarters for the Catholic Church in the United States?
No, although people sometimes think we are because of our location in the nation’s capital. The United States is divided into geographic areas called dioceses or archdioceses (an archdiocese is a significant or large diocese and is headed by an archbishop). The Archdiocese of Washington includes Washington, DC and five Maryland counties: Calvert, Charles, Montgomery, Prince George’s and St. Mary’s.
If you have a concern or question about the Church and don’t live within the Archdiocesan boundaries, the place you want to start is your parish and then, if you have further questions, the (arch)diocese serving your area....
Some of the things written in St. Blog's leave the impression the writers think the Archdiocese of Washington covers six city blocks along Pennsylvania Avenue, and that the job of Archbishop is to keep people elsewhere in the country informed of his conversations with government officials.